1. Field of the Invention
Example embodiments relate to semiconductor devices and methods of forming the same. More particularly, example embodiments relate to a semiconductor device including a self aligned plug and a method of forming the same.
2. Description of the Related Art
A conventional semiconductor device, e.g., a MOS transistor, may include a gate electrode with impurity regions formed on both sides of the gate electrode, so the impurity regions on both sides of the gate electrode may be used as source and drain electrodes, respectively. Voltages may be applied, e.g., independently, to the gate electrode, the source electrode, and the drain electrode via contact plugs to operate the semiconductor device.
As semiconductor devices become more highly integrated, however, it becomes difficult to form contact plugs for the gate, source and drain electrodes. In particular, the conventional contact plugs may be formed in respective contact holes, which may be patterned by using a photolithography to have a predetermined cross section. A reduced size of the semiconductor devices, however, may cause the patterned contact holes to have a modified predetermined cross-section, e.g., due to an optical proximity effect, thereby reducing a cross sectional area of the contact holes. A reduced cross sectional area of the contact holes may cause non-uniform deposition of metal therein, so a resultant contact plug may not completely fill the contact hole, and/or may increase resistance of the contact plugs therein, thereby reducing operability and reliability of the transistor.